Citizen Scientists Join Search for Earth-like Planets

As exoplanets pass in front of their host stars, they block some of
the star’s light, dimming it from our point of view here on
Earth. This dimming is what users will look for in the new online
citizen science project Planet Hunters. (Illustration: Haven
Giguere/Yale)

New Haven, Conn. — Web users around the
globe will be able to help professional astronomers in their search
for Earth-like planets thanks to a new online citizen
science project called Planet Hunters that launches Dec. 16. at
www.planethunters.org.

Planet Hunters, which is the latest in the Zooniverse citizen
science project collection, will ask users to help analyze data
taken by NASA’s Kepler mission. The space telescope has been
searching for planets beyond our own solar system—called
exoplanets—since its launch in March 2009.

“The Kepler mission has given us another mountain of data
to sort through,” said Kevin
Schawinski, a Yale University astronomer and Planet Hunters
co-founder. Schawinski also helped create the Galaxy Zoo citizen
science project several years ago, which enlisted hundreds of
thousands of web users around the world to help sort through and
classify a million images of galaxies taken by a robotic
telescope.

The Kepler space telescope is continually monitoring nearly
150,000 stars in the nearby constellation Cygnus, recording their
brightness over time. Astronomers analyze these images, looking for
any stars that show a slight dimming of their brightness. This
dimming could represent a planet passing in front of its host star,
blocking a tiny fraction of its light as seen from Kepler’s
vantage point in space. Those stars that periodically dim are the
best candidates for hosting relatively small planets that tightly
orbit their stars, similar to Earth.

“The Kepler mission will likely quadruple the number of
planets that have been found in the last 15 years, and it’s
terrific that NASA is releasing this amazing data into the public
domain,” said Debra
Fischer, a Yale astronomer and leading exoplanet hunter.
Although Planet Hunters is not tied directly to the Kepler mission,
the website will serve as a complement to the work being done by
the Kepler team to analyze the data.

Because of the huge amount of data being made available by
Kepler, astronomers rely on computers to help them sort through the
data and search for possible planet candidates. “But
computers are only good at finding what they’ve been taught
to look for,” said Meg
Schwamb, another Yale astronomer and Planet Hunters co-founder.
“Whereas the human brain has the uncanny ability to recognize
patterns and immediately pick out what is strange or unique, far
beyond what we can teach machines to do.”

After the success of the Galaxy Zoo project, the Yale team
decided to enlist web users once again to create what they hope
will become a global network of human computing power.

When users log on to the Planet Hunters website, they’ll
be asked to answer a series of simple questions about one of the
stars’ light curves—a graph displaying the amount of
light emitted by the star over time—to help the Yale
astronomers determine whether it displays a repetitive dimming of
light, identifying it as an exoplanet candidate.

“The great thing about this project is that it gives the
public a front row seat to participate in frontier scientific
research,” Schwamb said.

The possibility of Earth-like planets beyond our own solar
system has captured the collective human imagination for centuries.
Today, astronomers have discovered more than 500 planets orbiting
stars other than the Sun—yet almost all of these so-called
exoplanets are large gas giants, similar to Jupiter, which bear
little resemblance to Earth. Ever since the first exoplanet was
discovered in 1995, astronomers have raced to find ever smaller
planets closer to our own world.

“The search for planets is the search for life,”
Fischer said. “And at least for life as we know it, that
means finding a planet similar to Earth.” Scientists believe
Earth-like planets are the best place to look for life because they
are the right size and orbit their host stars at the right distance
to support liquid water, an essential ingredient for every form of
life found on Earth.

Yet Fischer is quick to caution that, even with the exceptional
data from the Kepler telescope, it will be extremely difficult to
pick out the weak signal created by such a small planet as it dims
its host star. “Planet Hunters is an
experiment—we’re looking for the needle in the
haystack,” she said.

Still, Galaxy Zoo proved that ordinary people can make
extraordinary discoveries. Several Galaxy Zoo users were listed as
co-authors on more than 20 published scientific papers that
resulted from the citizen science project, most of whom had no
prior knowledge of astronomy.

“The point of citizen science is to actively involve
people in real research,” Schawinski said. “When you
join Planet Hunters, you’re contributing to actual
science—and you might just make a real discovery.”